Method of making electrical contacts



June 29, 1965 c. B. GWYN, JR

METHOD OF MAKING ELECTRICAL CONTACTS 5 Sheets-Sheet 1 Filed Nov. 16,1960 June 29, 1965 c, w JR METHOD OF MAKING ELECTRICAL CONTACTS 3Sheets-Sheet 2- Filed Nov. 16, 1960 IN VEN TOR. LW/LQQAFJ 5. flay/15 m:

Arrmmos? June 29, 1965 c. B. GWYN, JR

METHOD OF MAKING ELECTRICAL CONTACTS 5 Sheets-Sheet :5

Filed NOV. 16, 1960 OOOOOOO \YWME M NH MW #7 M Ky W W W G, v Q fi C, Wmfil hm wm I!\ & \M\HIIIIH+ k i \L i -ww k k g j .DNJHINHNII UnitedStates Patent 3,191,273 METHOD OF MAKING ELECTRICAL (JGNTAC'IS ChildressB. Gwyn, Jr., Export, Pa., assignor, by mesne assignments, to Talon,Inc., a corporation of Pennsyl- Vilnla Filed Nov. 16, 1960, Ser. No. saw1 Claim. (c1. 29-15555 The present invention relates to processes formaking projection welding ty-pe composite contacts, and moreparticularly to such contacts in which a steel backing member isindented and has elements of contact element maerial placed therein.

A highly satisfactory type of electrical contact is one having a backingor support of relatively hard material, such as steel, with one face ofthis backing or support carrying a contact made of silver or the like.Such a contact is shown in my prior Patent No. 2,199,240.

Several methods are known by which the above described contact can bemade. In one known method, a button is provided by blanking and forminga contact from a sheet of clad or overlay material. That is to say, theinitial sheet may comprise steel with an overlay of silver. The contactproduced by this method is of satisfactory quality, but the method hasmany disadvantages, among which are a high scrap loss. In addition, inthis method, tolerances, materials temper and ratios of componentmaterials must be held to very exacting limits. These requirementsfurther increase the cost of the end product, so that all in all, thisprocess is a relatively expensive one.

In another known process, the backing metal members are first blanked orformed from steel strip, are then electroplated with nickel, copper orthe like, where desired, and then subsequently deposited into refractoryboats or jigs. The desired contact facing material, such as silver, isthen blanked from a sheet and placed upon the surfaces of the steelbacking members, which are usually disks, and then the refractory boator jig, loaded as described, is heated in an oven in order to fuse thesilver contact element to the steel backing member. This process, whichis described in my Patent No. 2,049,771 has been found to require arelatively large heating source, because of the refractory boat or jig.Since these boats or jigs generally are made of or contain carbon orgraphite mixtures, the steel backing members absorb some of the carbon,and this results in embrittlement, blistering, peeling, etc. Inaddition, it has been found that the contact facing material does notuniformly flow over the surface of the backing member, in all cases, andthis results in final products which have only a thin facing of contactmaterial near the outer edges thereof.

An object of the present invention is to provide a process formanufacturing composite contacts of satisfactory quality with economy ofcost.

Yet another object of the present invent-ion is the provision of aprocess for making composite contacts in which the use of refractoryboats or jigs is eliminated.

A further object of the present invention is to provide a process whichwill require the consumption of less heat than heretofore in order tomanufacture composite contacts.

A still further object of the present invention is the provision of aprocess for making composite contacts which will avoid the absorption ofcarbon or graphite, and thereby eliminate the production of contactsthat ar brittle, subject to blistering, peeling, etc.

ice

Another object of the present invention is to provide a process formaking composite contacts in which the contacts produced will have asuitably thick and uniform facing of contact material.

Other objects and many of the attendant advantages of the presentinvention will be readily understood from the following specificationand drawings, wherein:

FIGURE 1 is a plan view of a blank of weldable base material prepared inaccordance with the invention.

FIGURE 2 is a cross-sectional view showing the deposition of a contactelement in the sheet of FIGURE 1.

FIGURE 3 is an enlarged cross-sectional view of the structure shown inFIGURE 2, after heating.

FIGURES 4 through 8 are cross-sectional views illustrating successivesteps in the removal of an individual contact from the backing materialstrip.

FIGURE 9 is a cross-sectional view of the product produced by thisprocess.

FIGURE 10 is a cross-sectional View of the positioning of parts for themanufacture of a composite contact in accordance with another embodimentof the process of the present invention.

FIGURES 11, 12 and 13 are views showing successive steps in thetreatment of the parts shown in FIGURE 10, for the formation of acomposite contact, before heating.

FIGURE 14 is a cross-sectional view of the intermediate structure of thecomposite contact resulting from the step illustrated in FIGURE 13.

FIGURE 15 is a view similar to FIGURE 14, but showing the structureafter heating.

FIGURES 16 and 17 show steps in the process illustrating the removal ofa composite contact from the base material sheet.

Referring now to the drawings, wherein like or corresponding referencenumerals are used to designate like or corresponding parts throughoutthe several views, there is shown in FIGURE 1 a sheet 20 of weldablebase material, such as steel. Sheet 2% may be of any length, and inpractice the length of sheet or strip 20 is limited only by productionand transportation factors. The sheet 2t), which will be understood tobe a blank, has therein a plurality of indentations 21, the indentations21 being produced by known embossing or coining operations and beingcircular in the embodiment shown. There are a great number of theindentations 21 provided in the sheets 20, so that production mayproceed at a rapid rate.

Referring now to FIGURE 2, there may be seen in cross-section a part ofthe sheet 20, the indentation 21 being shown as having placed therein abutton or contact element 22 which is, conventionally, of silver.Whatever the materials of the sheet 20 and element 22, it will beunderstood that the element 22 will have a lower melting point than thesheet 20. It will be observed that the bottom wall 23 of indentation 21has a central depression 24 and a peripheral depression 25.

The entire sheet 20, or a suitable portion thereof, is, after beingloaded with the elements 22, passed into a furnace, the heat of whichmelts the element 22, and after cooling there is obtained a structurehaving the configuration shown in FIGURE 3. It will be noted that theelement 22 has melted and has filled the indentations 24 and 25, andthat the silver element 22 has crept up the walls of the indentation 21as is indicated at 26. There is also a convex upper surface 27 of themelted and solidified element 22.

Subsequent to the removal of the sheet 20, or a portion thereof, fromthe furnace, the steel grip may be passed shapes.

3 7 to a conventional punch press where the individual indentation 21with the melted and solidified element 22 will come under a punch 30which is above a coining die 31 in a die body 32. Punch 30 and die body32 will be caused to move towards each other viewing FIGURE 4, theaction continuing as shown in FIGURE wherein it may be seen that thepunch 30 has moved into contact with the sheet 20, entering into theindentation 21, while the coining die 31 has moved into position toreceive that material which will be punched from thesheet 20, andcomprising the melted and solidified contact element 22', together withthe indentation bottom wall 23.

FIGURE 6 showsthe shearing action completed, with separation of theparts from sheet and :FIGURE 7 shows the further progression of punchwhich now compresses the sheared element 22 and bottom wall 23 againstthe coining die '31 in die body 32. FIGURE 8 shows the upward movementof punch 30, and the downward movement of coining die 31, carrying withit'the completed composite contact 35. Contact 35 is shown in FIGURE 9,after having been removed from the coining die-31 as by blowing or thelike, and maybe seen to comprise a backing member 36 having a centralbutton 37, to the upper surface of which is-fused a generally arcuatesilver contact element 38, it being understood that the element 38 wasformerly the element 22 and that the backing member 36 formerly was thebottom wall 23 of indentation 21.

It will be understood, of course, that while the upper surface ofelement 38 is shown convex, and that this is due to the shape ofthepunch, 30, this shape is given by way of illustration only and whereother-shapes are desired the punch 30 may Referring now to FIGURES 10through 17, there is shown a further process in accordancewith theinvention,

there being seen in FIGURE 10 a sheet 40 which may be of steel or thelike, which sheet 40 is a backing'member and is positioned between a diebody 32 containing a coiningdie' 31 and a die body 42 having an'opening43 therethrough. Above the die body 42 having an opening 43the'rethrough. Above the die body 42, and conveniently placed in contacttherewith, is a sheet 45 which may be of silver or other suitablecontactelement material. In alignment with the aperture 43 and thecoining die 31 is a punch'30.

The punch 30 is caused to descend,-as is shown in FIGURE 11, so that itengages the sheet 45, and in passing throughthe aperture 43 shears adisk or button 46 from the sheet 45. The completed shearing action ofthe disk 46 is shown in FIGURE 12, where the punch 30 has continued itsdownward movement. StilI carrying before it the disk 46, the punch 30approaches and engages the backing sheet 40, and causes an indentationin-the backing sheet 40, as is shown in FIGURE 13. This indentation 47has the disk 46 therein, and becauseof. the

co-action and shape of the punch 30' and the coining die,

31, the sheet 40 will be embossed or. coined to providethe abovedimensioned indentation 47 As will be understood, while the punch 30moves downwardly, the coining" die 31 be provided with such other.

There may also be provided a convex surface, centrally located, as'at49. It will be understood that the partially completed product shown inFIGURE l5'is essentially the same as that shown in FIGURE 3, and thatthereafter there may be effected the same separating and coiningoperation as is shown in'tFIGURES 4 through 8. I

Alternatively, it is in some' instances desirable to continue thedownward motion of the punch 30 from the position shown in FIGURE 13, sothat the, disk 46 and the part of sheet 40, which ite'overlies and is incontact with are completely separated from the sheet-40, this be-."ing'shownin FIGURE -16. -Thepunch 30, having completed its punchingoperation is'shownmoving upwardly while the coiningidie 31 is shownmoving ina downward direction. Continued movement of -the coining die-31will carry it and the disk 46 and the part of sheet 40 to which'itis-adhered by pressing in a downward direction ==.so:that these partsare beneath the die body 32 (FIG- URE l7). Thereafter, the partiallyformed composite contact is'rernoved fromthe coining die31 and is heatedin a furnace so that the disk 46 melts and thereby is fused 'to thebacking member 50.

a In the process. above disclosed, due to the fact that theindentationsmaybe made and loaded, in such large quani tities and withsuch'great, rapidity as is provided by fast operating punching machines,the production of composite contacts may-proceed. at, ancextremely rapidrate.

This ,will substantially reduce the cost of the end productxFurther,-sinceit is unnecessary to provide jigs or boats which willconsumeheat and contaminate the contact elements, there is a furtheradvantage in the'economy of production and quality oftheend product.

It will be obvious tothose skilled in the art that various changes maybe made without departing from the spirit of the invention and,therefore,- the invention is not limited to what is shown in thedrawings'and'described; in ,the specification, but only as indicatedinthe appended :claims.

I claim: a A process for making projection welding composite electricali make-and-break, contacts which comprises:

will move upwardly as is indicated by the arrows in FIG- 7 URES "ll, 12and 13.

Subsequent to'the action and positioning of the parts into and againstthe metal of the indentation 47, and with silver disk 46 to its meltingpoint, so thatafter melting and resolidifying, the silver disk 46 'willhave the configuration shown in FIGURE 15, where it may be-seen thatthere is a creeping up the walls of the identation47 of the periphery ofthe silver, as is clearly shown at 48,

this having been obtained the entire sheet 40, or a suitable aportionthereof, is-placed in a'furnace to thereby heat the 7 (a)superposing asilver-contact facing, material blank and; aweldable steelbase material blank in spaced substantially parallel relation; a

' (b) moving at least one vpunch having a convex, central protuberanceand a convex peripheral protuberance through said contact facingmaterial blank to shear a" contact facing element therefrom, said facingelement being simultaneously deformed to conform: to' the shape of said,punch and including an outer facing having a convex central portion anda convex periphery;

(c)- moving a coiningdie, toward and into abutment with thexside of said;base material. blank opposite from said contact face material side;

-(d) moving I said punch toward the base material 1 blank toforce'said-contact facing element intothe blank and form an indentationtherein, including a bottom'wall having a central concave depressionformed by and superimposed with the convex central portion of saidfacingelement, and a peripheral concave depression formedrby andsuperimposed with the convex periphery of said facing element; (e)moving said punch away from the weldable base material blank todisengagethe punchifrom the facr ingelement seated in said blank;

(f) heating said base materialand saidfacingelement to liquefy saidfacing element and causerthe material thereof to flow along the walls ofthe indentation and fuse to the abutting base materiaL-the surface ofthe fused facing-element remote from the bottom a wall of-saidindentation being convex in shape and 7 having a peripheraledge defininga concave meniscus within said. indentation;

(g) moving a concave-shaped punch against each such composite fusedelement with a force sufficient to shear the same from the base materialblank, to provide the desired contact having a facing element ofsubstantially uniform thickness.

References Cited by the Examiner UNITED STATES PATENTS 6 Gwyn 29155.55Imes et a1. 29155.55 Gibbs 29-1 55 .5 5 High 29155.55 Sullivan 29-155.'55 Felts et a1 29-1{'55.55 Jones et al 29--155.55

WHITMORE A. WILTZ, Primary Examiner.

3/15 Eldred 200166 10 JOHN F. CAMPBELL, Examiner.

